Magnetic pulse welding (MPW) is a welding process that uses magnetic forces to drive two workpieces together, thereby welding the workpieces together.
Specifically, MPW involves a very high AC current that is passed through an inductive coil located near an electrically conductive material. Consequently, an intense magnetic field is locally produced that generates a secondary eddy current in the electrically conductive material. As a result, the secondary current generates a force which accelerates the electrically conductive material at a very high velocity toward a stationary material that is closely positioned in the trajectory of the electrically conductive material. In turn, the very high velocity produces an impact between the two materials, which in effect establishes a solid state weld between the electrically conductive material and the stationary material. Typically, the welds are achieved over a separation distance of only a few millimeters. For example, U.S. Pat. No. 7,015,435 to Yablochnikov, which is incorporated in its entirety herein, teaches the use of MPW.
As is the case for most welding operations, in order to produce a good weld, the attachment surfaces between the electrically conductive material and the stationary material must be clean. For example, in advance of the MPW operation, an acid is used to clean these surfaces of oil, which is followed by operations to rid the acid from the weld area and to allow time for the weld area to dry. Unfortunately, acid can leave residue, pits, and oxidation on the surfaces that can negatively affect the welding. Subsequently, these surfaces need further processing in order to remove any remaining residue that may have been left on the surfaces to be welded.
In addition, for the welding of tubular items, the wall thickness of the two materials must be appropriate to sustain a crush force that results from the acceleration of the electrically conductive material toward the stationary material. For the Yablochnikov patent, in order to assure a proper weld, the geometry is rather complex and thick (see, for example, FIGS. 19-25 of Yablochnikov), which in turn requires added power to produce an effective magnetic pulse weld.
Consequently, it would be beneficial to provide better conditions that would not require acid, abrasion, added processing time, complex geometry, more wall thickness, and higher power to produce. In turn, this should result in a faster production cycle time, lower material and labor costs, and a better quality part.